﻿[21] 
  ON 
  DEEP-SEA 
  DEPOSITS. 
  779 
  

  

  probable 
  that 
  sea 
  water 
  itself 
  may 
  have 
  some 
  effect 
  in 
  the 
  solution 
  of 
  

   carbonate 
  of 
  lime, 
  and, 
  further, 
  that 
  the 
  immense 
  pressure 
  to 
  which 
  

   water 
  is 
  subjected 
  in 
  great 
  depths 
  may 
  have 
  an 
  influence 
  on 
  its 
  chem- 
  

   ical 
  activity. 
  We 
  await 
  the 
  result 
  of 
  further 
  researches 
  on 
  this 
  point, 
  

   which 
  have 
  been 
  undertaken 
  in 
  connection 
  with 
  the 
  Challenger 
  reports. 
  

  

  We 
  are 
  aware 
  that 
  objections 
  have 
  been 
  raised 
  to 
  the 
  explanation 
  

   here 
  advanced 
  on 
  account 
  of 
  the 
  alkalinity 
  of 
  sea 
  water, 
  but 
  we 
  may 
  

   remark 
  that 
  alkalinity 
  presents 
  no 
  difficulty 
  which 
  need 
  be 
  here 
  consid- 
  

   ered 
  (Dittmar, 
  "Phys. 
  Chem. 
  Chall. 
  Exp.," 
  part 
  1, 
  1884). 
  

  

  This 
  interpretation 
  permits 
  us 
  to 
  explain 
  how 
  the 
  remains 
  of 
  Diatoms 
  

   and 
  Eadiolarians 
  (surface 
  organisms 
  like 
  the 
  Foraminifera) 
  are 
  found 
  in 
  

   greater 
  abundance 
  in 
  the 
  red 
  clay 
  than 
  in 
  a 
  Globigeriua 
  ooze. 
  The 
  

   action 
  which 
  suffices 
  to 
  dissolve 
  the 
  calcareous 
  matter 
  has 
  little 
  or 
  no 
  

   effect 
  upon 
  the 
  silica, 
  aud 
  so 
  the 
  siliceous 
  shells 
  accumulate. 
  Nor 
  is 
  

   this 
  view 
  of 
  the<case 
  opposed 
  to 
  the 
  distribution 
  of 
  the 
  Pteropod 
  ooze. 
  

   At 
  first 
  we 
  should 
  expect 
  that 
  the 
  Foraminifera 
  shells, 
  beiug 
  smaller, 
  

   would 
  disappear 
  from 
  a 
  deposit 
  before 
  the 
  Pteropod 
  shells; 
  bub 
  if 
  we 
  

   remember 
  that 
  the 
  latter 
  are 
  very 
  thin 
  and 
  delicate, 
  and, 
  for 
  the 
  quan- 
  

   tity 
  of 
  carbonate 
  of 
  lime 
  present, 
  offer 
  a 
  larger 
  surface 
  to 
  the 
  action 
  of 
  

   the 
  solvent 
  than 
  the 
  thicker, 
  though 
  smaller, 
  Globigeriua 
  shells, 
  we 
  shall 
  

   see 
  the 
  explanation 
  of 
  this 
  apparent 
  anomaly. 
  

  

  It 
  remains 
  now 
  to 
  point 
  out 
  the 
  area 
  occupied 
  by 
  the 
  red 
  clay. 
  We 
  

   have 
  seen 
  how 
  it 
  passes 
  at 
  its 
  margins 
  into 
  organic 
  calcareous 
  oozes, 
  

   found 
  in 
  the 
  lesser 
  depths 
  of 
  the 
  abysmal 
  regions, 
  or 
  into 
  the 
  siliceous 
  

   organic 
  oozes 
  or 
  terrigenous 
  deposits. 
  In 
  its 
  typical 
  form 
  the 
  red 
  clay 
  

   occupies 
  a 
  larger 
  area 
  than 
  any 
  of 
  the 
  other 
  true 
  deep-sea 
  deposits, 
  cov- 
  

   ering 
  the 
  bottom 
  in 
  vast 
  regions 
  of 
  the 
  North 
  and 
  South 
  Pacific, 
  Atlantic, 
  

   and 
  Indian 
  Oceans. 
  As 
  above 
  remarked, 
  this 
  clay 
  may 
  be 
  said 
  to 
  be 
  

   universally 
  distributed 
  over 
  the 
  floor 
  of 
  the 
  oceanic 
  basins, 
  but 
  it 
  only 
  

   appears 
  as 
  a 
  true 
  deposit 
  at 
  points 
  where 
  the 
  siliceous 
  and 
  calcareous 
  

   organisms 
  do 
  not 
  conceal 
  its 
  proper 
  characters. 
  

  

  Having 
  now 
  indicated 
  its 
  distribution, 
  we 
  must 
  consider 
  the 
  mode 
  of 
  

   its 
  formation, 
  and 
  give, 
  in 
  addition, 
  a 
  concise 
  description 
  of 
  the 
  miner- 
  

   als 
  and 
  of 
  the 
  organic 
  remains 
  which 
  are 
  commonly 
  associated 
  with 
  it. 
  

   The 
  origin 
  of 
  these 
  vast 
  deposits 
  of 
  clay 
  is 
  a 
  problem 
  of 
  the 
  highest 
  

   interest. 
  It 
  was 
  at 
  first 
  supposed 
  that 
  these 
  sediments 
  were 
  composed 
  

   of 
  microscopic 
  particles 
  arising 
  from 
  the 
  disintegration 
  of 
  the 
  rocks 
  

   by 
  the 
  rivers 
  and 
  by 
  the 
  waves 
  on 
  the 
  coasts. 
  It 
  was 
  believed 
  that 
  

   the 
  matters 
  held 
  in 
  suspension 
  were 
  carried 
  far 
  and 
  wide 
  by 
  currents, 
  

   aud 
  gradually 
  fell 
  to 
  the 
  bottom 
  of 
  the 
  sea. 
  But 
  the 
  uniformity 
  of 
  com- 
  

   position 
  presented 
  by 
  these 
  deposits 
  was 
  a 
  great 
  objection 
  to 
  this 
  view. 
  

   It 
  could 
  be 
  shown, 
  as 
  we 
  have 
  mentioned 
  above, 
  that 
  mineral 
  particles, 
  

   even 
  of 
  the 
  smallest 
  dimensions, 
  continually 
  set 
  adrift 
  upon 
  disturbed 
  

   waters, 
  must, 
  owing 
  to 
  a 
  property 
  of 
  sea 
  water, 
  eventually 
  be 
  pre- 
  

   cipitated 
  at 
  no 
  great 
  distance 
  from 
  land. 
  It 
  has 
  also 
  been 
  supposed 
  

  

  